﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace QFSW.QC.Utilities
{
    public static class ReflectionExtensions
    {
        #region Lookup Tables
        private static readonly Dictionary<Type, string> _typeDisplayNames = new Dictionary<Type, string>
        {
            { typeof(int), "int" },
            { typeof(float), "float" },
            { typeof(decimal), "decimal" },
            { typeof(double), "double" },
            { typeof(string), "string" },
            { typeof(bool), "bool" },
            { typeof(byte), "byte" },
            { typeof(sbyte), "sbyte" },
            { typeof(uint), "uint" },
            { typeof(short), "short" },
            { typeof(ushort), "ushort" },
            { typeof(long), "decimal" },
            { typeof(ulong), "ulong" },
            { typeof(char), "char" },
            { typeof(object), "object" }
        };

        private static readonly Type[] _valueTupleTypes =
        {
            typeof(ValueTuple<>),
            typeof(ValueTuple<,>),
            typeof(ValueTuple<,,>),
            typeof(ValueTuple<,,,>),
            typeof(ValueTuple<,,,,>),
            typeof(ValueTuple<,,,,,>),
            typeof(ValueTuple<,,,,,,>),
            typeof(ValueTuple<,,,,,,,>)
        };

        private static readonly Type[][] _primitiveTypeCastHierarchy =
        {
            new[] { typeof(byte),  typeof(sbyte), typeof(char) },
            new[] { typeof(short), typeof(ushort) },
            new[] { typeof(int), typeof(uint) },
            new[] { typeof(long), typeof(ulong) },
            new[] { typeof(float) },
            new[] { typeof(double) }
        };
        #endregion

        /// <summary>Determines if a type is a delegate.</summary>
        /// <returns>If the type is a delegate.</returns>
        public static bool IsDelegate(this Type type)
        {
            if (!typeof(Delegate).IsAssignableFrom(type)) { return false; }
            return true;
        }

        /// <summary>Determines if a type is a strongly typed delegate.</summary>
        /// <returns>If the type is a strongly typed delegate.</returns>
        public static bool IsStrongDelegate(this Type type)
        {
            if (!type.IsDelegate()) { return false; }
            if (type.IsAbstract) { return false; }
            return true;
        }

        /// <summary>Determines if a field is a delegate.</summary>
        /// <returns>If the field is a delegate.</returns>
        public static bool IsDelegate(this FieldInfo fieldInfo)
        {
            return fieldInfo.FieldType.IsDelegate();
        }

        /// <summary>Determines if a field is a strongly typed delegate.</summary>
        /// <param name="fieldInfo">The field to query.</param>
        /// <returns>If the field is a strongly typed delegate.</returns>
        public static bool IsStrongDelegate(this FieldInfo fieldInfo)
        {
            return fieldInfo.FieldType.IsStrongDelegate();
        }

        /// <summary>
        /// Determines if the type is a generic type of the given non-generic type.
        /// </summary>
        /// <param name="nonGenericType">The non-generic type to test against.</param>
        /// <returns>If the type is a generic type of the non-generic type.</returns>
        public static bool IsGenericTypeOf(this Type genericType, Type nonGenericType)
        {
            if (!genericType.IsGenericType) { return false; }
            return genericType.GetGenericTypeDefinition() == nonGenericType;
        }

        /// <summary>
        /// Determines if the type is a derived type of the given base type.
        /// </summary>
        /// <param name="baseType">The base type to test against.</param>
        /// <returns>If the type is a derived type of the base type.</returns>
        public static bool IsDerivedTypeOf(this Type type, Type baseType)
        {
            return baseType.IsAssignableFrom(type);
        }

        /// <summary>
        /// Determines if an object the given type can be casted to the specified type.
        /// </summary>
        /// <param name="to">The destination type of the cast.</param>
        /// <param name="implicitly">If only implicit casts should be considered.</param>
        /// <returns>If the cast can be performed.</returns>
        public static bool IsCastableTo(this Type from, Type to, bool implicitly = false)
        {
            return to.IsAssignableFrom(from) || from.HasCastDefined(to, implicitly);
        }

        private static bool HasCastDefined(this Type from, Type to, bool implicitly)
        {
            if ((from.IsPrimitive || from.IsEnum) && (to.IsPrimitive || to.IsEnum))
            {
                if (!implicitly)
                {
                    return from == to || (from != typeof(bool) && to != typeof(bool));
                }

                IEnumerable<Type> lowerTypes = Enumerable.Empty<Type>();
                foreach (Type[] types in _primitiveTypeCastHierarchy)
                {
                    if (types.Any(t => t == to))
                    {
                        return lowerTypes.Any(t => t == from);
                    }

                    lowerTypes = lowerTypes.Concat(types);
                }

                return false;   // IntPtr, UIntPtr, Enum, Boolean
            }

            return IsCastDefined(to, m => m.GetParameters()[0].ParameterType, _ => from, implicitly, false)
                || IsCastDefined(from, _ => to, m => m.ReturnType, implicitly, true);
        }

        private static bool IsCastDefined(Type type, Func<MethodInfo, Type> baseType, Func<MethodInfo, Type> derivedType, bool implicitly, bool lookInBase)
        {
            BindingFlags flags = BindingFlags.Public | BindingFlags.Static | (lookInBase ? BindingFlags.FlattenHierarchy : BindingFlags.DeclaredOnly);
            MethodInfo[] methods = type.GetMethods(flags);

            return methods.Where(m => m.Name == "op_Implicit" || (!implicitly && m.Name == "op_Explicit"))
                          .Any(m => baseType(m).IsAssignableFrom(derivedType(m)));
        }

        /// <summary>
        /// Dynamically casts an object to the specified type.
        /// </summary>
        /// <param name="type">The destination type of the cast.</param>
        /// <param name="data">The object to cast.</param>
        /// <returns>The dynamically casted object.</returns>
        public static object Cast(this Type type, object data)
        {
            if (type.IsInstanceOfType(data))
            {
                return data;
            }

            try
            {
                return Convert.ChangeType(data, type);
            }
            catch (InvalidCastException)
            {
                Type srcType = data.GetType();
                ParameterExpression dataParam = Expression.Parameter(srcType, "data");
                Expression body = Expression.Convert(Expression.Convert(dataParam, srcType), type);

                Delegate run = Expression.Lambda(body, dataParam).Compile();
                return run.DynamicInvoke(data);
            }
        }

        /// <summary>Determines if the given method is an override.</summary>
        /// <returns>If the method is an override.</returns>
        public static bool IsOverride(this MethodInfo methodInfo)
        {
            return methodInfo.GetBaseDefinition().DeclaringType != methodInfo.DeclaringType;
        }

        /// <summary>
        /// Gets if the provider has the specified attribute.
        /// </summary>
        /// <typeparam name="T">The attribute to test.</typeparam>
        /// <param name="provider">The attribute provider.</param>
        /// <param name="searchInherited">If base declarations should be searched.</param>
        /// <returns>If the attribute is present.</returns>
        public static bool HasAttribute<T>(this ICustomAttributeProvider provider, bool searchInherited = true) where T : Attribute
        {
            try
            {
                return provider.IsDefined(typeof(T), searchInherited);
            }
            catch (MissingMethodException)
            {
                return false;
            }
        }

        /// <summary>
        /// Gets a formatted display name for a given type.
        /// </summary>
        /// <param name="type">The type to generate a display name for.</param>
        /// <param name="includeNamespace">If the namespace should be included when generating the typename.</param>
        /// <returns>The generated display name.</returns>
        public static string GetDisplayName(this Type type, bool includeNamespace = false)
        {
            if (type.IsGenericParameter)
            {
                return type.Name;
            }

            if (type.IsArray)
            {
                int rank = type.GetArrayRank();
                string innerTypeName = GetDisplayName(type.GetElementType(), includeNamespace);
                return $"{innerTypeName}[{new string(',', rank - 1)}]";
            }

            if (_typeDisplayNames.ContainsKey(type))
            {
                string baseName = _typeDisplayNames[type];
                if (type.IsGenericType && !type.IsConstructedGenericType)
                {
                    Type[] genericArgs = type.GetGenericArguments();
                    return $"{baseName}<{new string(',', genericArgs.Length - 1)}>";
                }

                return baseName;
            }

            if (type.IsGenericTypeOf(typeof(Nullable<>)))
            {
                Type innerType = type.GetGenericArguments()[0];
                return $"{innerType.GetDisplayName()}?";
            }

            if (type.IsGenericType)
            {
                Type baseType = type.GetGenericTypeDefinition();
                Type[] genericArgs = type.GetGenericArguments();

                if (_valueTupleTypes.Contains(baseType))
                {
                    return GetTupleDisplayName(type, includeNamespace);
                }

                if (type.IsConstructedGenericType)
                {
                    string[] genericNames = new string[genericArgs.Length];
                    for (int i = 0; i < genericArgs.Length; i++)
                    {
                        genericNames[i] = GetDisplayName(genericArgs[i], includeNamespace);
                    }

                    string baseName = GetDisplayName(baseType, includeNamespace).Split('<')[0];
                    return $"{baseName}<{string.Join(", ", genericNames)}>";
                }

                string typeName = includeNamespace
                    ? type.FullName
                    : type.Name;

                return $"{typeName.Split('`')[0]}<{new string(',', genericArgs.Length - 1)}>";
            }

            Type declaringType = type.DeclaringType;
            if (declaringType != null)
            {
                string declaringName = GetDisplayName(declaringType, includeNamespace);
                return $"{declaringName}.{type.Name}";
            }

            return includeNamespace
                ? type.FullName
                : type.Name;
        }

        private static string GetTupleDisplayName(this Type type, bool includeNamespace = false)
        {
            IEnumerable<string> parts = type
                .GetGenericArguments()
                .Select(x => x.GetDisplayName(includeNamespace));

            return $"({string.Join(", ", parts)})";
        }

        /// <summary>
        /// Determines if two methods from different types have the same signature.
        /// </summary>
        /// <param name="a">First method</param>
        /// <param name="b">Second method</param>
        /// <returns><c>true</c> if they are equal</returns>
        public static bool AreMethodsEqual(MethodInfo a, MethodInfo b)
        {
            if (a.Name != b.Name) return false;

            ParameterInfo[] paramsA = a.GetParameters();
            ParameterInfo[] paramsB = b.GetParameters();

            if (paramsA.Length != paramsB.Length) return false;
            for (int i = 0; i < paramsA.Length; i++)
            {
                ParameterInfo pa = paramsA[i];
                ParameterInfo pb = paramsB[i];

                if (pa.Name != pb.Name) return false;
                if (pa.HasDefaultValue != pb.HasDefaultValue) return false;

                Type ta = pa.ParameterType;
                Type tb = pb.ParameterType;

                if (!ta.ContainsGenericParameters && !tb.ContainsGenericParameters)
                {
                    if (ta != tb) return false;
                }
            }

            if (a.IsGenericMethod != b.IsGenericMethod) return false;
            if (a.IsGenericMethod && b.IsGenericMethod)
            {
                Type[] genericA = a.GetGenericArguments();
                Type[] genericB = b.GetGenericArguments();

                if (genericA.Length != genericB.Length) return false;
                for (int i = 0; i < genericA.Length; i++)
                {
                    Type ga = genericA[i];
                    Type gb = genericB[i];

                    if (ga.Name != gb.Name) return false;
                }
            }

            return true;
        }

        /// <summary>
        /// Rebases a method onto a new type by finding the corresponding method with an equal signature.
        /// </summary>
        /// <param name="method">Method to rebase</param>
        /// <param name="newBase">New type to rebase the method onto</param>
        /// <returns>The rebased method</returns>
        public static MethodInfo RebaseMethod(this MethodInfo method, Type newBase)
        {
            BindingFlags flags = BindingFlags.Default;

            flags |= method.IsStatic
                ? BindingFlags.Static
                : BindingFlags.Instance;

            flags |= method.IsPublic
                ? BindingFlags.Public
                : BindingFlags.NonPublic;

            MethodInfo[] candidates = newBase.GetMethods(flags)
                .Where(x => AreMethodsEqual(x, method))
                .ToArray();

            if (candidates.Length == 0)
            {
                throw new ArgumentException($"Could not rebase method {method} onto type {newBase} as no matching candidates were found");
            }

            if (candidates.Length > 1)
            {
                throw new ArgumentException($"Could not rebase method {method} onto type {newBase} as too many matching candidates were found");
            }

            return candidates[0];
        }
    }
}